1. Field of the Invention
This invention relates to a foamed sealant composition and, more particularly, to such a composition which is especially useful for application to mine stoppings and other geological formations.
2. Description of the Prior Art
Sealants are often used to reduce or prevent the leakage of air and other gases through porous rock formations and structures. For example, in mining applications, sealants are commonly employed to consolidate and seal porous or cracked rock and broken strata to prevent the leakage of gas, such as methane gas, which if allowed to escape, would increase the risk of explosion and fire. In the same environment, sealants may be utilized to seal and minimize spalling and delamination of the ribs and roofs of mines and also to seal mine stoppings, i.e., walls constructed to close off unused tunnels. Stoppings are often installed in mines to direct air flow and control ventilation of the mine. Conventional stoppings constructed of concrete blocks and cement or sand bags, and the like, typically are not airtight. Therefore, sealants are employed to reduce or prevent air leakage through the stoppings which would otherwise interfere with the desired ventilation.
Sealants for the above-discussed purposes are disclosed, for example, in U.S. Pat. No. 4,607,066. These sealants contain various inorganic aggregates, including glass fibers, together with a cement. The sealant disclosed in U.S. Pat. No. 4,607,066 is described as a highly thixotropic composition comprising a water-soluble or water-dispersible polymeric binder, a filler material which is preferably inorganic and water. The binding agent is described as a dispersion of any polymer or copolymer which will dry to form a water-insoluble film such as polyethylene polymer, polystyrene polymer, polyacrylic polymer and polyvinyl acetate polymer having an average molecular weight of from about 10,000 to 10,000,000. The polymeric binder is combined with inert pigments or fillers.
Other sealants useful in mine applications are disclosed, for example, in British Patent No. 982,661 and U.S. Pat. No. 4,475,847. The sealants of British Patent No. 982,661 are described as fluid compositions comprising a natural or synthetic rubber such as polychloroprene, a latex or dispersion or a mixture of such latices and/or dispersions and a filler material. The sealants of U.S. Pat. No. 4,476,847 are described as comprised of polyisocyanate/polyol blends and a foaming agent whereby upon application of the sealant composition, consolidation and sealing of the geological formation is provided by means of the foaming and hardening of the polyisocyanate/polyol blend.